1. Field of the Invention
The present invention relates to a reinforcement fitting, and more specifically, to a reinforcement fitting to be installed to connections of existing, pipes such as underground water pipes for increasing the earthquake resistance.
2. Description of the Related Art
The longitudinal end portion of, for example, each of the underground water pipes has a joint structure for connecting other pipes, and via this joint structure, a plurality of pipes are connected one after another. Of the existing pipes set up throughout the country, part has a joint structure equipped with an aseismatic mechanism which can shrink and expand with pipe end portions allowed to maintain water-tightness, but the joint structure equipped with an aseismatic mechanism is not necessarily used in the connections of all pipes. Rather the joint structure without an aseismatic mechanism is mainly used in the underground water pipes today. In the case of the joint structure not equipped with the aseismatic mechanism, either one of the pipes comes off from the joint portion when large crustal movements such as earthquakes, etc. occur, and accidents such as water leakage, etc. occur. In countries where earthquakes are likely to occur, it is desirable to build all the connections of underground pipes of a pipe joint structure equipped with an aseismatic mechanism. In actuality, small part of the water pipes is now being replaced with joints equipped with an aseismatic mechanism.
However, the conventional joint structure equipped with the aseismatic mechanism has a complicated construction and is expensive, and is not always easy to install. In the case of cast iron pipes buried in earth over a long period of time, connection members such as bolts, nuts, etc. composing the joint structure may rust, and thus, even removal of these pipes involves hard and tiresome work. Consequently, it is technically and economically difficult and not realistic to replace all the connections of the existing pipes with the joint structure equipped with the aseismatic mechanism in a short time.
Therefore, development of reinforcement fittings has been strongly desired in order to provide an aseismatic mechanism to the connections of existing pipes with no aseismatic mechanism at high efficiency and at low cost. Under these circumstances, the object of this invention is to provide reinforcement fittings at high efficiency and at low cost to the connections of existing pipes.
The above object will be achieved by the inventions recited in the claims. That is, the reinforcement fitting according to this invention comprises an externally fitted portion which can provide shrink-expand capabilities with sealability held at connections between existing pipes to the connections of the existing pipes and has an inside diameter that can be externally fitted to the existing pipe, a contact member which is internally fitted to the recessed portion formed inside this externally fitted portion and has a tapered contact surface as well as a contact portion in contact with one of the existing pipes in the circumferential direction, and whose contact resistance with one of the existing pipes increases when an external force is exerted in the direction that separates the existing pipes, an engagement portion which can engage with a flange portion of the other existing pipe when the external force is exerted in the direction to separate the existing pipes.
Because the reinforcement fitting is configured in this way, the reinforcement fitting according to this invention is externally fitted over the whole connections in a manner to cover the connector from the outside without removing the connections of the existing pipes and with connections of the existing pipes held intact, and can be extremely easily installed. In addition, when the external force is exerted in the direction to separate the existing pipes due to crustal movement such as earthquakes, the aseismatic mechanism can be effectively exhibited by the action of the contact member which increases contact resistance, and the engagement portion and existing pipes contact with each other for the first time when the external force is exerted in the direction to separate the existing pipes, and therefore, it can exhibit function to permit shrinkage and expansion movement of the existing pipes. In addition, the cost can be held to a low level due to the simpler construction as compared to that of the conventional aseismatic joint equipped with shrink-expansion mechanism.
As a result, according to this invention, it is able to provide a reinforcement fitting that is able to give the aseismatic mechanism to the connections of existing pipes in high efficiency and at low cost.
The contact portion of the contact member forms an arc along the outer surface of the exiting pipe and has a V-shape in cross section. The contact member may be formed with a plurality of members which are placed in the recessed portion.
When configured in this way, if the reinforcement fitting is installed by externally fitting over the existing pipe, the contact portion of the contact member is able to be brought in line contact with the outer surface of the existing pipe, and this is desirable because the resistance to the travel direction of the existing pipes can be increased. In addition, because the cross section of the contact portion of the contact member has a nearly V-letter form, the contact portion cuts into the peripheral surface of the existing pipe when the reinforcement fitting is installed, and this is preferable because the resistance to the travel direction of the existing pipes can be increased, and in addition, because a plurality of contact portions exist, resistance against the travel of the existing pipe can be distributed, and this is desirable because the durability of the contact portion can be maintained in a high level.
In addition, it is preferable that the contact portion of the contact member is brought in contact with at least more than 30% of the circumferential length of the existing pipe.
If configured in this way, resistance to the travel action of the existing pipe can be constantly maintained high. If the length in contact with the existing pipe is less than 30% of the circumferential length of the existing pipe, the contact resistance to the earthquake which may exert a large external force is small and this is not desirable. It is still more preferable that the contact portion of the contact member be in contact with more than 80% of the circumferential length of the existing pipe.
Furthermore, when the reinforcement fitting is installed to the connections of the existing pipes, it is preferable that the tip end of the engagement portion be formed to have sufficient length that can reach the vicinity of the tip end of the other existing pipe in the axial direction of the existing pipe.
Because it is configured in this way the flexibility allowance corresponding to the travel enable distance of the existing pipe against the external force to separate the existing pipes can be maximized with the water tightness maintained.